I have always had issues with citing sources. In the old days it was easier. We just used what the teacher or professor told us and the format wasn't that specific. Nowadays, there is MLA, APA and other formats that have to be used, plus you have web sites, blogs, and online magazines to cite. Here are some sites that can help you with your citing and research. (all are free).
Son of Citation Machine - this cite is very easy to use. You click on the type of formatting you want to use (MLA, APA, Turabian, or Chicago) then the type of resource (email, web site, book, encyclopedia, and many, many more) then fill out the web form with the info required and it will create the citation for you. Very powerful and easy to use.
bibme is another easy to use citation resource. You can search for a book, website, etc. or enter the information yourself and even create a bibliography on the site and then download it in one of four formats (MLA, APA, Turabian, or Chicago). It supports lots of types of resources, like books, websites, films, newspapers, and more.
Purdue University Owl - The Owl Online Writing Lab from Purdue University has help and instructions for citing different resources in different formats (MLA, APA and Chicago), as well as help in conducting research and using the research. It does not create your citations, but shows you the correct format.
Zotero - Zotero is another nice tool for research and citation. It allows you to collect, organize, cite, and share your resources in different formats (MLA, APA, Chicago and more.) It is a download, not a web app and integrates with Word and OpenOffice. It does sync your data online so you have access from any computer and even from mobile devices.